Recent advances in photocatalyst sheet development and challenges for cost-effective solar hydrogen production

Abstract

Solar hydrogen production by photocatalytic water splitting is studied to solve energy and environmental problems. It is estimated that practical implementation of this technology will require a photocatalytic water splitting system that is not only highly efficient in solar-to-hydrogen energy conversion but also cheap and scalable. Particulate photocatalyst sheets based on immobilized particulate semiconductors are a promising approach to meet these requirements owing to their scalability without sacrificing their intrinsic water splitting activity. Nevertheless, existing sheet systems have not reached the targeted solar-to-hydrogen energy conversion efficiency yet. This is because the quality of narrow-bandgap photocatalyst materials has not been sufficiently improved, and also because methods for activating such photocatalysts in warm water under ambient pressure, which is assumed to be a practical outdoor operating condition, while suppressing reverse reactions have not been sufficiently developed. This perspective describes recent advancements in photocatalyst sheets and panel reactor systems intended for practical implementation of solar hydrogen production via the overall water splitting reaction, and discusses issues regarding the development of photocatalytic systems that can produce solar hydrogen with satisfactory performance.